To my understanding, military members on Permanent Change of Station (PCS) orders are exempt from being considered an importer of firearms. That's what allows service members to bring their personally owned firearms (baring any outlawed features, etc). If that is true, could they "import" BX-25's from out of state and keep them for personal use?

I don't plan on doing this, just trying to figure out the mess if the California system. I walked into a sporting goods store this week in Wisconsin and walked out with a new Savage Mk II thirty minutes later, so all these restrictions are confusing.

Your understanding is incorrect. A military member on PCS orders is considered a resident of the state, and relinquishes certain things from their home state, such as firearms purchases. Technically if you PCS to Cali, you can't go on leave and buy a gun in your home state.

That doesn't stop people from doing do. But it is technically illegal. Likewise, when PCSing with firearms, you're not importing because you're moving. You're supposed to fill out the DOJ form for off roster handguns, I'm not sure about any other paperwork.

You can't bring listed assault weapons like the AR-15s so most people strip the lower and sell it out of state before moving, then buy a stripped ca lower. I believe >10 mags must be disassembled but I'm not positive.